Differential cylinder-piston assembly



May 2, 1950 R. s. HoAR ET A1.. 2,505,771

DIFFERENTIAL CYLINDER-PISTON ASSEMBLY www ay 2, T950 R. s. HoAR ET AL 2,505,771

DIFFERENTIAL CYLINDER-PISTON ASSEMBLY Filed June 16, 1948 2 Sheets-Sheet 2 force than in the first portion of the stroke. Exhaust from the upper end of upper and lower chambers l5a and ib passes out through ports l5a and |519 respectively. This continues for the remainder of the upward stroke. During this upper portion of the piston stroke, the two cylinder-piston assemblies operate together in parallel.

The reverse motion (downward) is similar, pressure being against the upper instead of the lower faces of the pistons. Initially (Figure 2) fluid under pressure is admitted, through ports l5a and |512, into the upper end of lower and upper chambers lea and lb respectively; and exhaust from the lower end of chambers ita and |61) passes out through ports lia and ilib respectively, these chambers being interconnected through liuid conduit lia and port 24a. Accordingly, during the first (upper) portion of the downward stroke (Figure 2), the cylinder-piston assembles operate in parallel, and the effective pressure area is the eiiective area of upper piston Ib plus the eiective area of lower piston Ilia. When lower piston iso. passes port Efira, however, pressure uid is introduced, through fluid conduit Ila, into the lower end of upper chamber lGb, thereby equalizing the pressure on the upper face of lower piston lea and the lower face of upper piston |81). Accordingly, for the remainder of the downward stroke (Figure 1), the cylinderpiston assemblies operate in series, and the eective pressure area is the area of upper piston Iib alone. Both speeds for the downward stroke are slightly higher and less forceful than the corresponding speeds of the upward stroke, due to piston rod IQ which reduces slightly the effective pressure area of the pistons.

Turning now to Figures 3 and 4, showing a second embodiment of our invention, we see that it differs from the first embodiment shown in Figures 1 and 2 in that:

(1) Lower and upper cylinders ila and IIb contain a fixed axial rod 25 which is rigidly connected to lower end plate I'Ea and intermediate plate I3', and contains huid conduit lla' and ports 24a and Mb', as well as port l5a and a portion of iiuid conduit lib' leading thereto.

(2) Piston rod I9 and pistons Iiia and lSb' are annular in form (instead of in the form of a solid rod) to permit them to embrace fixed rod L 25. That portion of annular rod iii between the pistons |811. and lh is preferably connected to the outer periphery of the pistons and has sliding Contact with the cylinder walls in order to Other parts of the cylinder-piston assembly of our second embodiment are similar to corresponding parts of the first embodiment, and bear the same reference numbers with the addition of a prime.

The operation of the second embodiment is the same as the iirst.

Having now described and illustrated two forms lof our invention, we wish it to be understood that our invention is not to be limited to the specific Aform or arrangement of parts herein described and shown.

At the top of fixed We claim:

1. In a cylinder-piston assembly, the combination of a rst cylinder having a first chamber with a first piston therein; a second cylinder having a second chamber with a second piston therein; a piston rod; means operatively connecting the two pistons to the piston rod; means for alternatively admitting pressure fluid to one or the other end of the first cylinder, and for simultaneously permitting exhaust from the opposite end of the first cylinder; a fluid conduit between one end of the first cylinder chamber and the corresponding end of the second cylinder chamber; and a second fluid conduit between the other end of the second cylinder chamber and a point intermediate the ends of the first cylinder chamber whereby the effective pressure area of the assembly is automatically increased when the first piston travels past said point in one direction, and is automatically reduced when the first piston travels past said point in the other direction.

2. A cylinder-piston assembly according to claim 1, further characterized by the fact that the irst and second pistons are connected in tandem.

3. A cylinder-piston assembly according to claim 2, further characterized by the fact that the first and second pistons have the same effective pressure area.

4. A cylinder-piston assembly according to claim 3, further characterized by the fact that the rst and second pistons are axially aligned.

5. A cylinder-piston assembly according to claim 4, further characterized by the fact that the first and second cylinders abut each other end-to-end, and have a common fluid-tight wall separating their respective chambers.

6. A cylinder-piston assembly according to claim 5, further characterized by the fact that the means operatively connecting the two pistons is a piston rod centrally disposed along the longitudinal axis of the pistons and extending through and having a huid-tight sliding contact with said wall.

7'. A cylinder-piston assembly according to claim 6, further characterized by the fact that said intermediate point is located in the outer wall of said first cylinder.

8. A cylinder-piston assembly according to claim l, further characterized by the fact that the rst and second pistons have the same effeci tive pressure area.

9. A cylinder-piston assembly according to claim 1, further characterized by the fact that the first and second cylinders abut each other end-to-end, and have a common fluid-tight wall i separating their respective chambers.

1G. A cylinder-piston assembly according to claim 9, further characterized by the fact that the means operatively connecting the two pistons is an annular piston rod extending through and having fluid-tight sliding Contact inwardly and outwardly with said wall.

1l. A cylinder-piston assembly according to claim l0, further characterized by the fact that the annular piston rod has duid-tight outwardly 1 sliding contact with the inner surface of the first cylinder.

12. A cylinder-piston assembly according to claim l, further characterized by the fact that said iirst and second cylinders have an interior longitudinal xed rod rigidly connected to the 75 ends of said cylinders.

13, A cylinder-piston assembly according to claim 12, further characterized by the' fact that the means operatively connecting the two pistons is an annular piston rod extending through and having fluid-tight sliding contact inwardly and outwardly with said wall.

14. A cylinder-piston assembly according to claim 13, further characterized by the fact that one of said fluid conduits extends within Said longitudinal iixed rod.

15. In a cylinder-piston assembly, the combination of a pair of double-acting cylinder-piston assemblies; a first work attachment; a second work attachment; a piston in each assembly operatively connected to the rst work attachment; a cylinder in each assembly operatively connected to the second work attachment and having a chamber for said piston of its respective assembly; a pair of interconnected fluid ports, one for one end of each of said chambers; a second pair of fluid ports, one for the other end of each of said chambers; a fth port intermediate the ends of one of said chambers; and means connecting said i'ifth port with one of Said second pair of ports.

16. A cylinder-piston assembly according to claim l5, further characterized by the fact that the chambers are axially aligned and have a uniform transverse cross-sectional area.

17. In a cylinder-piston assembly, the combination of: a pair of double-acting cylinder-piston assemblies; each including a piston and a cylinder providing a pressure chamber for the piston; means operatively connecting each piston to a common work attachment; means operatively connecting each cylinder to a second common work attachment; and fluid conduits connecting in parallel a portion of said chambers corresponding to a portion of the piston stroke, and connecting in series another portion of said chambers corresponding to another portion of the piston stroke.

18. A cylinder-piston assembly according to claim 17, further characterized by the fact that said uid conduits include a first fluid conduit interconnecting one end of said chambers; and a second fluid conduit connecting the other end ol' one of said chambers and a point intermediate the ends of the other of said chambers.

19. A cylinder-piston assembly according to claim 18, further characterized by having a iirst fluid port for the first uid conduit; a second fluid port at the other end of said other of said chambers; and means for alternatively admitting pressure fluid to the first or the second of said fluid ports; and for simultaneously permitting exhaust from the other of said iiuid ports.

ROGER SHERMAN I-IOAR. JOHN ADAMS THIERRY.

No references cited. 

